In the new material system, aerogel, with its unique nano-porous structure, has become a core material in the field of energy conservation and thermal insulation. However, its insufficient mechanical properties, especially the low tensile strength, have always been a bottleneck for its large-scale application. A large number of studies and practices have shown that fiber reinforcement is the most effective way to improve the tensile strength of aerogel, and the fiber length is the core parameter for regulating the reinforcement effect. This paper deeply analyzes the correlation between the two from three dimensions: microscopic mechanism, performance rules, and process control. 
Microscopic action mechanism: Length determines the enhancement efficiency
The tensile failure of aerogels is attributed to the brittle fracture of the nano-skeleton. The addition of fibers, essentially, is to construct a "second-phase network" to bear and disperse the external force. 
Short fibers (< 5mm): They are in an isolated state in the matrix and can only impede crack propagation by anchoring at the ends, with a limited range of effect. 
Medium and long fibers (5-20mm): They form a penetrating network, with the physical entanglement between fibers and the chemical bonding with the matrix working together. During stretching, the fibers transfer stress through the interface bonding, achieving "cooperative force-bearing", which significantly enhances the strength. 
Super-long fibers (>20mm): Uneven dispersion leads to agglomeration, creating stress concentration points and instead undermining the structural integrity. 
Performance variation law: Quantitative analysis of length effect
When the fiber volume fraction is 15%: 
Length 3mm: tensile strength 0.35 MPa, increased by 25%. 
Length 10mm: tensile strength 0.92MPa, increase of 85%. 
Length 18mm: tensile strength 1.05MPa, increase of 98%. 
Length 25mm: tensile strength 0.88 MPa, decreased by 16%. 
It can be seen that the 10-15mm range is the golden interval for fiber length, balancing strength and processability. 
Key points of process control: 
Fiber pretreatment: Surface silane modification to enhance the interfacial bonding strength with aerogel. 
Dispersing process: High-speed shear dispersion to ensure uniform distribution of medium and long fibers; 
Compound proportion: The fiber length and diameter are matched (length-to-diameter ratio of 500-1000), achieving the best reinforcing effect. 
Application Value and Industry Significance
Precise control of fiber length transforms aerogel from a "fragile material" into a "high-performance structural insulation material". The aerogel product uses 12mm custom ceramic fibers, with a tensile strength of 1.1MPa, and can be applied in scenarios such as pipelines, equipment, and new energy battery packs. 
Fiber length directly determines the tensile strength of aerogels by regulating the micro-network structure. Short fibers are inefficient, ultra-long fibers are counterproductive, and medium to long fibers are highly effective.